The apparatus of the present invention is intended for use with certain types of packaging machines, being especially packaging machines for packaging e.g soft-drink cans into cardboard carriers.
These packaging machines have a carrier magazine, in which the carriers are stacked in an unopened condition. The packaging machine is arranged to pick the cardboard carriers off the magazine one by one, to unfold and open up the picked carrier so that the carrier presents e.g six receptacles, then to place the opened six-pack carrier on a conveyor, then to lower six soft drink cans into the six receptacles, and then to convey the six packs away for sale.
The packaging machine with which the apparatus of the present invention is mainly intended for use includes also a carrier-picker, which functions to pick the next carrier from the magazine. The carrier-picker serves to pick the as-yet-unopened carriers out of the magazine on a one-and-only-one basis. The designer has to be careful to ensure that only one carrier is picked, since picking either no carrier, or two carriers, can be highly disruptive to the operation of the packaging machine.
The accuracy with which the carrier-picker carries out its one-and-only-one function depends not only on the structure of the carrier-picker, but also on the manner in which the magazine presents the carriers to the carrier-picker. Simply providing that the magazine does not run out of carriers during operation is not enough: the designer should ensure that the carriers in the magazine are urged towards the carrier-picker always with the same force, or at least approximately the same force. If the stack of carriers in the magazine were pressed hard against the carrier-picker one minute, and then pressed only lightly towards the carrier-picker the next minute, that might well lead to erratic performance of the carrier-picker, and to the one-and-only-one function being compromised.
The apparatus of the present invention has, as a main function, the automatic replenishment of the carrier magazine with fresh carriers. The carriers are shipped and delivered to the factory in which the packaging machine is located, in cardboard shipping-boxes, and it is one of the functions of the present apparatus to extract the fresh carriers from the shipping boxes, and to insert them into the magazine.
It is an aim of the invention to accomplish the automatic replenishment in a manner that permits the magazine to continue to maintain an approximately-constant force on the carrier picker, during replenishment. It would not be acceptable for the replenishment apparatus to require the packaging machine to be stopped, in order to permit routine replenishment.
It is also an aim of the invention to provide an apparatus which can be adapted for use with a number of different kinds of magazines and packaging machines.
It is also an aim to provide an apparatus that, having been fitted to a particular machine, can be adjusted for different requirements. For example, the packaging machine may be set up to package six-packs of beer bottles on Monday, and to package twelve-packs on Tuesday. Not only are the carriers different, but Tuesday""s carriers might also be orientated, in their shipping boxes, upside-down with respect to Monday""s.
It is also an aim to provide an apparatus which will enable trouble-free replenishment of carrier magazines over a long service period. Since factory machinery can be dangerous for operatives and others, it is also an aim to provide an apparatus in which the possibility of injuries to workers (and damage to the apparatus) is minimised.
In the apparatus shown in U.S. Pat. No. 6,213,707, the shipping box suction head was conveyed on a travelling track, and the movements of the bucket included only pivoting about a fixed pivot. In the present apparatus, the bucket not only pivots, but travels vertically, on a bucket-elevator. The suction-head may also be on an elevator, but, as will be described, the required motions of the suction-head can now be accommodated by a swing-lever about a fixed pivot axis.
In the present apparatus, the carriers are extracted from the box by pulling the box straight up out of the bucket. In the present apparatus, preferably the box is held steady by the suction head, and the bucket is lowered in the elevator, to achieve the linear extraction motion relatively between the box and the bucket. The bucket moves downwards in a linear motion, preferably with no arcuate component. The movement of the bucket on the elevator is vertical, or nearly vertical.
The inclusion of the bucket-elevator means that the conveyor for the incoming full boxes of carriers, and the conveyor for the outgoing empty boxes, are well above the height of the magazine. Generally, the magazine is at e.g waist height, since the magazine is a critical component that needs to be carefully set up by the assembly-line setter. Of course, the conveyors also are subject to being adjusted and maintained, but it is recognised as preferable not to compromise the access and space around the magazine, and this preference can be accommodated when the conveyors can be positioned well above the magazine.
In the present apparatus, the full-box-conveyor does not need to be within arc-swing distance of the magazine, as was the case in ""707. The empty-box-conveyor does have to be within arc-swing distance of the elevator, but that is not a very demanding restriction, by comparison.
Of course, the box conveyors should not be too far up above the magazine. The carriers go through the carrier-picker at a rate of, say, one per second. There may be as few as fifty carriers in a box, which means the cycle time for replenishing the magazine with fresh carriers has to be accomplished well within fifty seconds. But having the bucket travel through a vertical height of a meter or two is easily accommodated within the allowable cycle time.
The carrier-picker at the end of the magazine of carriers must pick carriers from the magazine on a one-and-only-one basis. The accuracy of the carrier-picker is affected by the force with which the carriers are pressed against the carrier-picker. That force should be kept reasonably constantxe2x80x94and it is not acceptable for the carrier picker to stop picking carriers from the magazine while the magazine is being replenished. The row of carriers is biassed towards the carrier picker by means of weights, or a pneumatic ram, or the equivalent. But the biassing device has to be withdrawn during replenishment. As noted in U.S. Pat. No. 6,213,707, there is enough compressive resilience in the row of carriers on the magazine to keep the carriers pressing constantly against the carrier picker, even though the biassing device has been withdrawn, if hooks or fingers are provided to stop the row of carriers from easing away from the carrier-picker.
The force with which the carriers press against the carrier-picker can be maintained more nearly constant, if the quantity of carriers per box is small. Thus, frequent transfers of a small number of carriers to the magazine is preferred over the less frequent transfer of a larger number. It is preferred that the boxes should contain, typically, no more than about two hundred carriersxe2x80x94because then the difference in the magazine, between xe2x80x9cjust filledxe2x80x9d, and xe2x80x9cfilling now requiredxe2x80x9d, might be too much, whereby the carrier picker might start to function erratically. On the other hand, the boxes should not contain less than about fifty, or cycle times become too rapid and jerky for the kinds of motions required.
Whatever the number of carriers in a box, preferably the whole quantity should be transferred to the magazine in one go. It can be awkward to handle the carriers if the quantity has to be split after taking the stack out of its shipping box.
The arrangement of the apparatus as described herein permits the pivot axis of the bucket to run through the centre of gravity of the loaded bucket, or close to it. This keeps centrifugal forces on the contents of the bucket to a minimum, permitting fast motions. It also means that the arc-swing of the bucket about its axis is minimised, which is useful in tight spaces. It also means that no counterweights are needed for the bucket.